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This paper addresses calculation of current Total Harmonic Distortion (THD) for a three-phase two-level PWM inverter with an LCL-filter. Analytical approach introduced in late 1980s for a two-level inverter with inductance dominated load is generalized accounting for the smoothing effect of an LCL-filter. Though the obtained closed-form analytical solutions initially assume (infinitely) large ratio...
Capacitor-switching operation can be used to measure network harmonic impedance. Via the transient components of voltage and current after capacitor switching, the harmonic impedance of PCC (Point of Common Coupling) can be calculated. To improve measurement accuracy, the TLS-ESPRIT algorithm is introduced in this paper to filter out noise and fundamental components in voltage and current signals...
An effective auxiliary flyback circuit to suppress voltage ripple is proposed and investigated in a single-phase isolated full-bridge boost power factor correction (PFC) converter, by which the output voltage ripple can be suppressed obviously. The output voltage ripple can be reduced by adding the auxiliary link using the absorbed energy from the voltage spike. The energy is controlled to be transferred...
The benefits of using grid connected Voltage Source Converters (VSC) related to processing and improving of electrical power quality in distribution grid heavily depends on current control (CC) method. Research in this field are mainly focused on response dynamics, stability and accuracy of reference current tracking under strongly distorted grid voltage conditions with variable grid impedance in...
Harmonic resonance problems can be aroused in the industrial power system in the presence of both nonlinear loads and shunt capacitors. This paper investigates the harmonic resonance problem by case-studying of a copper smelting plant low voltage power distribution system. A flexible selective harmonic compensation and resonance damping algorithm for shunt active power filter (SAPF) is proposed to...
This paper presents a comprehensive study about a Simplified Rail Power Conditioner (SRPC) based on a half-bridge indirect AC/DC/AC Modular Multilevel Converter (MMC) and a V/V traction power transformer. The proposed system with a half-bridge MMC can decrease the costs, reduce the control complexity, and require less hardware devices in comparison with the rail power conditioner based on a full-bridge...
The search of efficient, robust and fault-tolerant electronic power converters is a challenge for the industry and academia. Nowadays, the integration and exploitation of the renewable energy sources and energy storage systems is required. In these terms, the multilevel power converters and specifically the cascaded H-bridge (CHB) power converter is a very good candidate. However, if a CHB power converter...
A novel switching power loss estimation method for modular multilevel converters (MMCs) with the nearest level modulation (NLM) is introduced in this paper. It focuses on the switching actions caused only by change of the inserted submodule (SM) number per arm, named as the essential switching transitions. Every essential switching action can be identified under the assumption of ideal sinusoidal...
The modular multilevel converter (MMC) is considered to be the state of the art in medium- and high-voltage application. The nearest level modulation (NLM) method is one of the most popular modulations, however, when applied to MMC with small number of sub-modular (SM), the output waveforms contain large harmonic components. This paper proposes a modified NLM method. By changing the traditional rounding...
Although the mechanism of electric energy flow for nonsinusoidal conditions is well described today, so fare is not yet available a generalized power theory, and theoretical calculations for the design of such devices as active filters or dynamic compensators. Therefore the task of designing compensators for optimize energy transmission with nonlinear time-varying loads in nonsinusoidal regimes is,...
A novel approach for mitigation of power quality issues have been presented in the paper. This paper introduces a Center-Point-Clamped AC-AC Buck-Boost Converter based power quality device for industrial and residential customers at the leaf end of the distribution network. This converter utilizes the principle of center-point-clamping to reduce the voltage stress on the power semiconductor switches...
This paper presents a new application of modular multilevel cascaded converters (MMCC) for combined active harmonic current elimination and reactive power compensation in a power distribution line. A technique for simultaneous extracting harmonic components and reactive element in the load current is presented. A novel voltage control scheme for balancing the module intra-cluster capacitor voltages...
The increasing number of renewable energy sources and their integration into the medium voltage grid leads to an increasing interest in multilevel structures for the interfacing power electronic converters. A feasible topology for MV applications is the Stacked Multicell Converter (SMC) offering a modular structure and several voltage levels. A robust control, current limiting strategies under grid...
The authors have proposed the single-stage bidirectional buck AC/DC converter. This paper presents comparison of loss and volume between the proposed single-stage buck AC/DC converter and the conventional two-stage AC/DC converter. The effectiveness of the proposed single-stage buck AC/DC converter is verified by experiments.
This paper proposes a novel discontinuous PWM (DPWM) in order to reduce dc-link current harmonics of a voltage source inverter (VSI) over wide load-power-factor range. This modulation method, which requires only one carrier, contributes to a lifetime extension of smoothing capacitors in a motor drive system. Furthermore, by realizing this modulation method with only one carrier, a high cost hardware...
This paper presents a mmW frequency generation stage aimed at minimizing phase noise via waveform shaping and harmonic extraction while suppressing flicker noise upconversion via proper harmonic terminations. A second-harmonic tank resonance is assisted by a proposed embedded decoupling capacitor inside a transformer for shortest and well controlled common-mode current return path. Class-F operation...
This paper presents a boost switched-capacitor nine-level single-phase inverter, which utilizes flying capacitors and an H-bridge. Besides the boosting ability, the inverter is capable of producing redundant switching states that are used as a degree of freedom in controlling the voltage of DC link capacitor. A comprehensive study of the theoretical aspects of the proposed structure and its practical...
This paper presents a new modulation concept for three-to-single-phase direct AC/AC modular multi-level converter-based railway interties. The concept minimizes the inherent harmonic coupling between the two grid sides and is therefore particularly suited to operation at very low cell numbers and switching frequencies. Moreover, it facilitates the use of specific modulation methods, such as optimized...
This paper examines resonant characteristics of the transmission line compensated with the Static Synchronous Series Compensator. Frequency-domain characteristics of the line impedance are studied to evaluate whether the SSSC can cause electrical resonance in the line, hence the potential to excite subsynchronous resonance (SSR) in neighboring turbine-generator plants. Detailed studies are performed...
The problems associated with the harmonics needs more attention as more number of distributed generators like PV and wind are integrated into a distribution system. Although the integration presents a lot of benefits, satisfying the needs of local load requirements by reducing the line losses and facilitating congestion management, the problems of power quality that impact the distribution system...
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